1. Field of the Invention
This invention relates to electroluminescent display devices and methods of making the same, and more particularly to slidebase, plug-in type devices that use light-emitting diode chips and replace on a one-to-one basis switchboard, key button or similar lamps. As used herein, electroluminescent refers to radiation from electrically excited solid state elements.
2. Description of the Prior Art
Light-emitting diodes of the prior art have been used in making slidebase, plug-in type devices that replace on a one-to-one basis switchboard, key button or similar lamps. Such light-emitting diode devices offer a number of advantages over the conventional carbon and tungsten filament switchboard lamps. These advantages include greatly reduced power consumption, less burn hazard to personnel and materials such as plastics, much longer life, higher reliability and reduced maintenance costs.
However, these prior art devices are expensive owing to a considerable degree to costly prior art assembling techniques that involve complex, tedious, time consuming manual and single-device processing operations. Such prior art devices have either not been assembled in a lead-frame environment or only partially assembled in such an environment, and this has added to their assembling cost. Also contributing to the expense of these prior art devices is the high cost of the piece parts going into the completed assembly.
Other disadvantages of the prior art devices include their lack of compactness and ruggedness. They are susceptible to coming apart; for example, various metal-to-metal and plastic-to-metal bonds have broken.
Still another disadvantage of the prior art devices is their tendency to freely rotate in their sockets, and this on occasion results in their failure to make proper contact for their energization.
In assembling these devices, it is desirable to eliminate as many of the complex, tedious and time consuming manual operations as possible, to assemble these devices in a lead-frame environment using batch processing to the greatest extent possible and at the same time to overcome the above-described disadvantages.
It is also desirable to have the energization of a light-emitting diode device indicate the opening of a protective element by an overload condition in a circuit to which the element is connected, such energization making it readily apparent that such overload condition has occurred. On the other hand, it is difficult in many of the prior art devices to determine if such an overload condition has occurred because it is often not readily apparent that a protective or fusible element has opened a circuit to which it is connected. This problem is compounded when there are many protective elements in the same housing or terminal box, and only one has been subjected to an overload condition, and it therefore is necessary to determine which element of many has been subjected to this condition.